Electronic access control device

ABSTRACT

An electronic lock utilizes two microprocessors remote from each other for enhanced security. The first microprocessor is disposed close to an input device such as a keypad, and the second microprocessor is disposed close to the lock mechanism and well protected from external access. The first microprocessor transmits a communication code to the second microprocessor when it receives via the input device an access code that matches a preset access code. The second microprocessor opens the lock if the transmitted communication code matches a preset communication code. The dual-microprocessor arrangement is advantageously used in a voice controlled access control system and in a motorcycle ignition control system. The present invention further provides an electronic access control system which has a master electronic key having a preset number of access, and an electronic alarm system for a bicycle that has a remote control mounted in the helmet of the rider.

RELATED APPLICATION

[0001] This application is a continuation-in-part of copending U.S.patent application Ser. No. 08/339,555 of Denison et al., entitled“ELECTRONIC ACCESS CONTROL DEVICE UTILIZING A SINGLE MICROCOMPUTERINTEGRATED CIRCUIT,” filed on Nov. 15, 1994.

FIELD OF THE INVENTION

[0002] This invention relates generally to access control devices, andmore particularly to electronic access control devices controlled bymicroprocessors.

BACKGROUND OF THE INVENTION

[0003] An electronic access control device, such as an electroniccombination lock or an electronic alarm system, allows the user toactivate or deactivate the access control without the use of theconventional key and mechanical lock mechanism. With the development ofmicroprocessor integrated circuits, it is becoming common to implementmicroprocessor-based control circuitry in electronic access controldevices. Electronic access control devices are known, for example, fromU.S. Pat. No. 5,021,776. In this device, and other common electronicaccess control devices, a microprocessor is used in combination with akeypad and an electrically programmable read only memory (EPROM). Themicroprocessor compares the combination entered in the keypad by theoperator with the combination stored in the EPROM. If the twocombinations match, the microprocessor opens the lock.

[0004] There are problems associated with previous electronic accesscontrol devices. One area of problems concerns the manufacture of thedevices, including the difficulty in programming the non-volatilememory, such as the EPROM, for storing the access code and other usefulinformation for the operation of the device. EPROMs, which usuallyrequire parallel programming, interrupt the manufacturing process inthat they restrict when the manufacturer can program the device. Amanufacturer would prefer to program the access code into the EPROM asthe last step in the manufacturing process. However, with parallelEPROMs, burning in the code after the device has manufactured isdifficult. After the device is soldered together, the manufacturer mustcontend with integrated circuit pin clips and must worry aboutinterference with other circuitry on the manufactured device. Further,manufacturing, with known electronic access control devices, requiresmany pin connections which increase manufacturing cost.

[0005] Related to the problems associated with the pin connections ofthe microprocessor integrated circuit (IC) is the concern of devicereliability and ease of use. When the device contains a significantnumber of pin connections, the reliability of the device decreases.Further, serial access to the EPROM to determine the electronic accesscode is easier than parallel access in terms of pin connections. Whenthe user forgets or loses the access code in the EPROM, a locksmithcould plug into the device and retrieve the access code serially withoutbreaking into the safe. However, with parallel EPROMs, serial access isnot available.

[0006] One common problem associated with previous electronic locks istheir potential vulnerability to tampering. A conventional electroniclock receives an access code via an input device such as a keypad orelectronic key reader, verifies the access code, and then energizes asolenoid, relay, motor, or the like to open the lock. This arrangementis vulnerable to tampering because if the control circuit is somehowbroken in or removed, one can open the lock by “hot-wiring” the controllines for activating the lock-opening mechanism.

[0007] Another technically challenging problem is related to the need toprovide electrical energy to power the operation of the electronicaccess control device. For many applications, it is desirable to use aportable energy source, such as a battery, to power the access controldevice. A battery, however, has a rather limited amount of electricalenergy stored therein. Thus, it is extremely important to reduce thepower consumption of the control circuit and peripheral devices of theaccess control device to extend the service life of the batteries.

[0008] For instance, it is typical to use a solenoid-operated lock in anelectronic lock. The power consumed by the solenoid in opening the lockis quite significant. Thus, the battery can be rapidly drained by therepeated operation of the solenoid. As another example, it is common toinclude a low-battery detection circuit in an electronic lock to providea warning signal to the user when the battery voltage falls below apredetermined level. The operation of the low-battery detection circuit,however, also consumes electrical energy and contributes to the drainingof the battery.

[0009] Some electronic locks are provided with electronic keys. When anelectronic key is presented to a key reader of an associated electroniclock, it transmits an access code to the electronic lock. By using anelectronic key, the user does not have to enter manually the access codeby means of a keypad. In certain applications, a remote control unit isused which has a radio transmitter to send the access code to the lockwithout direct electrical contact with the electronic lock.

[0010] Although electronic keys are a convenient feature, they havetheir associated problems. One problem is related to the unauthorizeduse of the keys. For example, many hotels provide safes equipped withelectronic locks in their hotel rooms. Such safes typically allow thehotel guests to set their own access codes. In cases where the hotelguests forget the access codes they set, the hotel management has tosend someone with a master key which has a master access code storedtherein to open the safes. There is a danger that such a master key maybe used for unauthorized opening of other safes in the hotel.

[0011] Another problem associated with the use of an electronic key or awireless access code transmitter is that the key or the transmitter maybe lost easily, or the user may simply forget to bring the key ortransmitter. This problem is especially serious if the electronic accesscontrol device does not provide other means, such as a keypad, forentering the access code.

SUMMARY OF THE INVENTION

[0012] It is a general object of the present invention to develop anelectronic access control device which is easier to manufacture and morereliable to operate, and provides improved security to prevent tamperingor unauthorized access.

[0013] It is an object of the present invention to provide an electronicaccess control device with a non-volatile memory for storing an accesscode that permits the manufacturer of the device to easily insert theaccess code into the device and then read out the code for verification.

[0014] It is an object of the present invention to provide an electronicaccess control device that provides significantly enhanced security andreduced vulnerability to tampering as compared to previous electroniclocks.

[0015] It is an object of the present invention to develop an electronicaccess control device which has fewer total components and pinconnections for smaller device area and greater reliability.

[0016] It is another object of the present invention to develop anelectronic access control device with a solenoid-operated lock which hasreduced power consumption by reducing the power used in operating thesolenoid.

[0017] It is a related object of the present invention to develop anelectronic access control device that has an improved low-batterydetection circuit which has minimized energy consumption.

[0018] It is a more specific object of the present invention to providean electronic alarm system for a bicycle that uses a wirelesstransmitter for sending an access code for activating and deactivatingthe alarm system and that is configured to help the rider of the vehicleto prevent losing the transmitter or forgetting to bring thetransmitter.

[0019] It is another more specific object of the present invention toprovide an electronic access control system with a master key for aplurality of remote electronic locks that effectively prevents theunauthorized use of the master key.

[0020] The present invention accomplishes these and other objects andovercomes the drawbacks of the prior art. First, there is provided anelectronic access control device which reduces the number of pinconnections required to manufacture, to read, to program, and to operatethe device. The device multiplexes the inputs and outputs of themicroprocessor IC so that a single pin can function as an input in onemode and an output in another. The microprocessor determines, based onthe mode of operation, whether a pin functions as an input or an output.

[0021] The electronic access control device of the present invention hasa communication port connected to selected pins of the microprocessor ICfor accessing the non-volatile memory for storing an access code.Through the communication port, the manufacturer can interact with themicroprocessor to store an access code into the non-volatile memory andretrieve the access code for verification. By virtue of the provision ofthe communication port, the factory-programmed access code can be savedinto the non-volatile memory after the control circuitry is completelyassembled.

[0022] In one embodiment, the electronic access control device has amicroprocessor IC with a plurality of pins, a keypad for inputtinguser-entered access codes and a non-volatile memory, such as an EEPROM,external of the microprocessor for storing an access code. At least oneof the IC pins is connected to both the keypad and the non-volatilememory for receiving the user-entered code from the keypad andtransferring data between the IC and the memory.

[0023] In accordance with the object of the invention to reduce thevulnerability to tampering, the present invention provides an electronicaccess control device which has two microprocessors. The firstmicroprocessor is preferably disposed close to the user interface suchas a keypad or an electronic key reader. The second microprocessor ispreferably disposed close to the lock mechanism and substantiallyshielded from external access. When the first microprocessor receives auser-entered code, it compares the entered code to a stored access code.If those two codes match, the first microprocessor transmits a specialcommunication code to the second microprocessor. The second IC opens thelock if the transmitted communication code matches a storedcommunication code. Since the second IC is well protected from externalaccess, the risk of tampering by hard-wiring is significantly reduced.

[0024] This dual-microprocessor arrangement is advantageously used in avoice activated access control system which has a first microprocessorcircuit having speech recognition capability, and a secondmicroprocessor circuit which carries out a commanded operation whenreceiving a correct communication code from the first microprocessorcircuit. The first microprocessor circuit may include a transmitter forwireless transmission of the communication code.

[0025] The dual-microprocessor arrangement is also advantageously usedin a motorcycle ignition switch control system for turning onaccessories or starting the engine in response to the ignition keyposition.

[0026] The present invention also provides an effective solution to theproblem associated with the intensive need for power of the solenoid. Inthe present invention, the electronic access control device pulses thepower to the solenoid so that the overall power consumption in operatingthe solenoid is lower. Thus, the battery has a longer life and the lockhas an increased number of accesses.

[0027] In accordance with a related aspect of the present invention, theelectronic access control device employs a low-battery detection circuitthat is turned off and therefore consumes no electrical power when themicroprocessor is in the sleep mode. The low-battery detection circuituses a combination of a voltage divider and a transistor to compare thebattery voltage and the regulated voltage for determining whether thebattery voltage is low, and uses another transistor in series with thevoltage divider to selectively turn the current through the voltagedivider on and off. When the current through the voltage divider is off,the low-voltage detection circuit does not consume electrical energy.

[0028] In the case of an electronic access control system with a masterkey and a plurality of remote electronic locks, the present inventioneffectively prevents unauthorized use of the master key. In accordancewith the present invention, the master key has a master access code anda number of access stored therein. Each of the remote electronic lockhas a key reader to communicating with the master key. When anelectronic lock detects in the key a correct master access code and anumber of access that is at least one, it opens the associated lock anddecrements the number of access in the key by one.

[0029] In accordance with another aspect of the present invention, thereis provided an electronic alarm system for a bicycle or a similarmanually powered vehicle. The alarm system includes a remote controlunit installed in the helmet of the rider of the bicycle, and anelectronic alarm installed on the bicycle. The remote control unit has atransmitter for the wireless transmission of control signals to activateor deactivate the alarm on the bicycle. The alarm on the bicycleincludes a motion detector for sensing the movement of the bicycle. Ifthe motion detector detects the movement of the vehicle when theelectronic alarm is activated, the alarm is set off.

[0030] It is a feature of the present invention to mount the remotecontrol in the helmet of the rider of the bicycle. By virtue of thisarrangement, the rider is more likely to remember to wear the helmet.The risk of losing the remote control is also substantially eliminated.

[0031] These and other features and advantages of the invention will bemore readily apparent upon reading the following description of thepreferred embodiment of the invention and upon reference to theaccompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a perspective view showing an electronic access controldevice having a keypad;

[0033]FIG. 2 is a block diagram of the electronic access control deviceof FIG. 1;

[0034]FIG. 3 is the schematic of the electronic access control device;

[0035]FIG. 4 is the flow chart at power-up of the device;

[0036]FIG. 5 is the flow chart of the device in normal operation;

[0037]FIG. 6 is a block diagram of a remote access control device;

[0038]FIG. 7 is a schematic of the input electronics of the remoteaccess control device of FIG. 6;

[0039]FIG. 8 is a schematic of another embodiment of the electroniccontrol access device which has a non-volatile memory sharing certainpins of a microprocessor with a keypad;

[0040]FIG. 9 is a functional block diagram showing an embodiment of anelectronic access control device having two microprocessorscommunicating with each other to provide enhanced security of thedevice;

[0041]FIGS. 10A and 10B are schematic views together showing anapplication of the dual-microprocessor configuration of FIG. 9 in anelectronic combination lock;

[0042]FIG. 11 is a functional block diagram showing an application ofthe dual-microprocessor configuration of FIG. 9 in an ignition controlsystem for a motorcycle;

[0043]FIG. 12 is a functional block diagram showing an application ofthe dual-microprocessor configuration of FIG. 9 in a voice controlledaccess control device;

[0044]FIG. 13 is a functional block diagram showing another embodimentof the voice controlled access control device;

[0045]FIG. 14 is a functional block diagram showing another embodimentof the voice controlled access control device which has a centralcontrol station and remote devices;

[0046]FIG. 15 is a schematic view showing an electronic access controlsystem which has a master key for opening a plurality of remoteelectronic locks; and

[0047]FIG. 16 is a schematic view of an electronic alarm system for abicycle which has a remote control unit mounted in a riding helmet andan electronic alarm mounted on the bicycle.

[0048] While the invention is susceptible of various modifications andalternative constructions, certain illustrated embodiments hereof havebeen shown in the drawings and will be described below. It should beunderstood, however, that there is no intention to limit the inventionto the specific forms disclosed, but, on the contrary, the invention isto cover all modifications, alternative constructions and equivalentsfalling within the spirit and scope of the invention as defined by theappended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] Referring to the drawings, there is shown in FIG. 1 anillustrative electronic access control device 10 having a keypad 11,light emitting diodes (LEDs) 12 and 13, and a mechanical lever arm 14.In this illustration, the device is used as a lock for an office safe.The device can also be applied to various applications including locksfor vending machines or amusement games.

[0050] The main components of the electronic access code device areshown in FIG. 2 which include a keypad 11, a microprocessor 14, anaccess code input and output 15, an acoustic output (a piezo ceramicbender, Model No. KB1-1541) 16, LEDs 12 and 13, a voltage regulator(LM2936Z-5.0) 17, a battery 18, an electromechanical driver output 19,an oscillator 20, and a reset circuit 21. Inputs to the device may takethe form of a thumbprint scan, a retinal scan, or a magnetic strip inputwhich may work in conjunction with a keypad or as a sole means of input.Outputs may take the form of an alpha-numeric display which may work inconjunction with an acoustic output or an LED or as a sole means ofoutput.

[0051] The manufacturers which provide microprocessors applicable to thedevice include: Micro-Chip (PIC 16C54, PIC 16C57, PIC 16C71, PIC 16C76);Motorola (MC68HC705J1, MC68HC705K1, MC69HC705P6, MC68HC705P8,MC68HC705P9); National Semiconductor (COP 820C); SGS-Thomson (ST 6210);Texas Instruments (370C311); Zilog (Z84C01).

[0052] A more detailed schematic of the device is shown in FIG. 3,highlighting the reduced pin configuration and the serial access to theelectrically programmable read only memory (EPROM) 22. Several of thepins on the microprocessor 14 are multiplexed and perform multiplefunctions, at times used as inputs and at times used as outputs;thereby, the pin configuration is able to use only 9 pins for the keypadinput, the acoustic output, and the EPROM 22 reading and writing. Forexample, the 12 keypad entries are shown in rows and columns. Eachkeypad entry in a row is connected to the corresponding pin. Forexample, keypads “3”, “6”, and “911” are connected to pin R1. Eachkeypad entry in the same column is connected to a corresponding pin aswell. For example, keys “3”, “0”, “1”, and “2” are all connected to pinC3.

[0053] The multiplexing of the keypad allows for input of twelvedifferent inputs (“0” through “9”, PROG, and CLR) using a four by threeconfiguration, as shown in FIG. 4 and FIG. 5. In particular, there arefour rows and three columns in this configuration. In accordance withanother embodiment, a keypad with four different inputs allows for aslittle as a two by two configuration through multiplexing the inputs.

[0054] The following example will illustrate the multiplexing withrespect to the keypad 11. Normally, in sleep mode, pins R1, R2, R3 andR4 are waiting for an input. When, for example, the keypad “3” is input,pin R1, which keypad “3” is connected to, is triggered signifying to themicroprocessor 14 that an interrupt has occurred. The microprocessor 14then executes an interrupt in the software program and changes one ofthe four pins (R1, R2, R3 and R4) into an output whereby a logic high issent to the R1 pin. When a keypad is pressed, it acts as a shortcircuit;.thus, when the microprocessor 14 sends out a logic high, itthen senses pins C1, C2 and C3 to determine exactly which keypad in therow has been pressed. In this case, where keypad “3” is input, C3 ishigh. Pressing keypad “3” acts as a short circuit so that when R1 issent high, there is a direct electrical connection between pin R1 and C3via keypad “3”. Thus, the microprocessor 14 can determine that keypad“3” was pressed based on R1 and C3 both being logic high.

[0055] Another example of using multiple functions as connected to asingle pin is the acoustic output 16. The acoustic output 16 isconnected, via a transistor, to pin C2. Pin C2 is also connected tokeypads “CLR”, “4”, “5”, and “6”. When the microprocessor 14 sends anaudible signal output, pin C2 acts as an output. When the microprocessoris sensing the keypad input, C2 acts as an input.

[0056] A further example of multiple functions as connected to a singlepin is the EPROM 22 sensing function. The EPROM 22, as shown in FIG. 3,is part of the microprocessor 14. The DATA line (bidirectional in thatthe line is able to input data to write and output data to read) andCLOCK line of the EPROM 22 are connected to C1 and C2, respectively.Pins C1 and C2 are connected to the keypad as well. When the PROGRAMsignal is input, C1 and C2 function as inputs when writing to the memorylocation in the EPROM and function as outputs when reading from thememory location in the EPROM 22. Through this arrangement, themanufacturer may serially program the device with the access code. Themicroprocessor 14 uses registers 56 to transmit the incoming serial datainto parallel data for the EPROM 22 to input. Further, the end user mayread the EPROM 22 access code serially as well. In reading the EPROM 22,only three pins must be accessed (PROGRAM, DATA, and GROUND). Themicroprocessor 14 uses registers 56 to transmit the outgoing paralleldata from the EPROM 22 to serial form for output.

[0057] It will be appreciated that by installing a communication port,namely the access code I/O 15, in the microprocessor-based controlcircuit, the manufacturer of the device can access the EPROM byinteracting with the microprocessor 14 via the communication port. Byvirtue of this arrangement, the manufacturer can program the access codeinto the EPROM as the last step in the manufacturing process, i.e.,after the control circuit has been fully assembled. Thus, there is nolonger the need to use a EPROM that is pre-programmed with access codes,or to attempt to input the access code into the EPROM by means of pinclips or the like during the manufacturing process. This ability toprogram the EPROM after the completion of the control circuit impartssignificant flexibility, efficiency, and reliability to themanufacturing process.

[0058] The operation of the electronic access code device is shown inflowchart form in FIG. 4 and FIG. 5. FIG. 4 shows the initializationsequence of the device upon power-up 24. The microprocessor, whichcontains an EPROM 22 and a random access memory (RAM) 23, checks to seeif there is an access code stored 25 in the EPROM 22. The microprocessor14 performs this operation by checking if a proprietary bit sequence isset, wherein the particular sequence of bits signifies that the EPROM 22has a stored access code. If the bit sequence is present, the EPROM 22contains the access code, whereby the microprocessor 14 waits for inputfrom the keypad or waits for an external read signal 26 from themicroprocessor 14.

[0059] If the bit sequence is not present, the EPROM 22 does not containthe access code in its memory. The microprocessor 14 must then wait forthe external program signal 28 which signifies that the access code isbeing written to the EPROM 22. The external program signal, as shown inFIG. 3, is labeled PROGRAM and is connected to pin IO4 and pin IRQ ofthe microprocessor 14. In this mode, when the PROGRAM signal is toggled,this signifies that the access code is being burned into the EPROM 22.The microprocessor 14 then uses the CLOCK and DATA lines to clock in thedata thereby reading the access code. Then, the microprocessor 14 storesthe access code into memory 30. The microprocessor 14 subsequently setsthe proprietary bit sequence on the EPROM 22 signifying that the EPROM22 contains the access code. Finally, the microprocessor 14 waits forinput from the keypad or waits for an external read signal 26 from themicroprocessor 14.

[0060] The EPROM 22 can also be used to store features other than theaccess code. It can be used to determine such things as: (1) the amountof time the solenoid 31 is to be energized upon opening the lock; (2)the number of key presses in the access code; (3) the option ofdisabling the permanent access code temporarily when a new- access codeis stored in RAM 23; (4) the device serial number; and (5) the date andtime the device was manufactured or put in service. These features allowthe manufacturer to deliver to an original equipment manufacturer (OEM)customer a generic electronic lock assembly. The OEM customer may thencharacterize all the specific lock features at the OEM customerfacility.

[0061] As shown in FIG. 5, after the power-up initialization routine,the microprocessor waits for an entry from the keypad 32. Severalfunctions are available based on the keypad entry. If the program key(PROG key) is first pressed, the operator wishes to input an additionalaccess code 33. In this mode, the microprocessor 14 inputs the next fivenumbers from the keypad 34, 35, 36, 37, and 38. The comparator 57,within the microprocessor 14, compares the two numbers and checks if theinput number matches the access code 39 from the EPROM 22 which isstored in RAM 23. If the two numbers match, this signifies that theoperator knows the access code in the EPROM 22 and therefore hasclearance to input an additional access code 40. Thus, themicroprocessor accepts the next five numbers from the keypad as theadditional access code 41, 42, 43, 44, and 45, and stores the new accesscode 46 in RAM 23. The operator may then input either the access codefrom the EPROM 22 or the additional access code to open the lock. Theoperator may repeat this procedure and place additional access codesinto RAM 23. The additional access codes will be stored in RAM 23 untilthe power is removed from the microprocessor 14 at which time the RAM 23memory will be lost.

[0062] An alternate mode of using the PROG key is to disable thepermanent access code in the EPROM 22 temporarily when a new access codeis entered into RAM 23. After the PROG key is hit, the microprocessor 14inputs the next five numbers 34, 35, 36, 37 and 38. The comparator 57,within the microprocessor 14, compares the input number with thepermanent access code 39 from EPROM 22. If the two numbers match, themicroprocessor 14 inputs a second access code 41, 42, 43, 44, 45. Inthis alternative, when the microprocessor 14 stores in RAM 23 the newaccess code 46, it disables access to the permanent access code in RAM23. Therefore, until the battery 18 is turned off, the only access codeavailable is the new access code stored in RAM 23.

[0063] If an operator enters the PROG key at any time other than at thefirst keypad entry from sleep mode, the microprocessor will display theerror message 47 by sounding the acoustic output 16 through pin C2 andthe LED 13.

[0064] If a number from the keypad 11 is first entered while in sleepmode 48, the microprocessor 14 waits until another four numbers areentered 49, 50, 51, and 52, from the keypad 11. The microprocessor 14then compares the number entered from the keypad 11 with the access code53 stored in RAM 23. If the numbers match, the microprocessor 14energizes the solenoid 31 at the output 54. The microprocessor 14 canalso energize a DC motor, an electromechanical relay, or a solid-staterelay. If the numbers do not match, the error message is sent 47 bysounding the acoustic output at pin C2.

[0065] If the clear key on the keypad is entered at any time in theoperation of the device, the microprocessor 14 waits 5 seconds beforegoing back into sleep mode and waiting for the next keypad entry.

[0066] One feature of the device is a lockout of keypad operations. Ifthe microprocessor 14 receives three consecutive operations whichgenerate error messages 47, the microprocessor 14 will disable operationof the device for two minutes. Any attempt to operate the device in thetwo minute lockout period will generate an error message 47.

[0067] An additional feature of the system is a requirement that a digitmust be entered within a specified time. Otherwise, the microprocessor14 will send an error message 47 if there is a five second lapse betweenkeypad entries.

[0068] A further feature of the system is the modulated voltage acrossthe solenoid 31. When the correct access code is input 53 from thekeypad 11, the microprocessor 14 energizes the solenoid 31. Themicroprocessor 14 must supply sufficient power to the solenoid to unlockthe lock (i.e., the solenoid must push the plunger in against the coilto open the lock). This involves two different operations. First, thesolenoid 31 must physically push the plunger against the coil. Second,the solenoid 31 must keep the plunger pushed against the coil for thespecified time in which to keep the lock unlocked.

[0069] The first operation (pushing the plunger) is very energyintensive. The solenoid 31 must exert kinetic and potential energy tophysically move the plunger against the coil. The second operation(maintaining the position of the plunger) is less energy intensive. Thesolenoid 31 must exert only potential energy in terms of keeping theplunger compressed against the coil. The device, in order to unlock thelock, supplies the entire battery power necessary for the solenoid 31 topull the plunger in against the coil. The microprocessor 14 accesses thetimer 55, within the microprocessor 14, whereby the timer indicates whento reduce the power. Once the plunger is pulled in, the microprocessor14 modulates the voltage to the solenoid 31. This reduces the currentinto the solenoid while the solenoid plunger is held in since the entireDC current is not required to keep the plunger in the closed positionrelative to the coil. This in turn reduces the total amp-hours ofcurrent out of the battery during an access cycle, and the total numberof accesses to the device increases.

[0070] By way of example, the solenoid 31 requires 300 milliamps ofcurrent to pull the plunger in. The microprocessor 14 accesses the timer55, waiting 0.5 seconds to do that operation. The microprocessor 14 thendrops the solenoid current to 150 milliamps. This current is sufficientfor the solenoid 31 to keep the plunger flush against the coil. Themicroprocessor 14 accesses the timer 55 again, waiting for the timer 55to indicate that three seconds have passed, supplying the lower currentto allow the user to open the door. In this manner, the microprocessor14 uses approximately ½ as much power in the modulated mode.

[0071]FIG. 6 highlights another aspect of the invention, the remoteoperation of the electronic access code device using a battery. Thedevice can be integrated with other electronic devices forming a systemof electronic locks. At the center of the system is a central controlstation whereby each of the devices may be accessed.

[0072] The accessed device is designed for low power consumption so thatit may operate on a battery for an extended period of time. The remoteaccess device is normally in a sleep mode. In other words, the device isnot in active operation. The remote device can “wake-up” from the lowpower sleep mode in a variety of ways. One method is for the circuitryin the sleep mode device to sense the incoming signal. When the signalis sent, the remote device resumes normal operation. Another method isfor the circuitry in the sleep mode device periodically to resume normaloperation and sense if there is an incoming signal. If the incomingsignal is sent, the circuitry is able to receive the bitstream data thatcontains the access code. The circuitry thus remains in a low-powersleep-mode condition for the majority of the time, dissipating lowpower, while no signal is received. The device may then be powered by abattery.

[0073] The remote electronic access code device is divided into twoparts: the input electronics 60 and the processing electronics 64. Theprocessing electronics 64 contains a microprocessor, an access codeinput and output, an acoustic output, light emitting diodes (LED), avoltage regulator, and an electromechanical driver output. Thus, theremote device is similar to the microprocessor in processing the inputaccess code, as shown in FIG. 1, except the access code may be input inseveral ways. In this embodiment, the data stream is input serially intothe microprocessor 14 so that a variety of serial inputs may beconnected to the input of the microprocessor 14. For example, the accesscode may be input using a traditional keypad 11 transmitting data inserial mode. Moreover, the data may be input serially using anelectromagnetic signal input from the radio frequency (RF), opticalfrequency or infrared frequency bands. Thus, the microprocessor 14, inthis configuration, may accept the input from any one of this inputs.

[0074] The input electronics 60 accepts the code sent from the centralcontrol. The method of transmitting the code may take several formsincluding an electromagnetic signal (such as a RF signal sent by an RFserial bitstream transmitter, or an infrared signal) or a data line(telephone line).

[0075] When an RF signal is used, the central station transmits a signalvia a transmit antenna 63 (transducer that sends radiatedelectromagnetic fields into space). The radiated waves containing the RFsignal contains the bitstream access code which is sent to the inputelectronics 60. The input electronics 60 contains the RF wake-up 61 andthe RF decode circuitry 62. In one embodiment, the RF wake-up circuit 61is ordinarily in a low power sleep-mode. However, for a 10 millisecondperiod every 1 second, the RF wake-up circuit 61 senses for an RFbitstream signal. If an RF bitstream signal exists, it remains awake andreceives the entire RF bitstream signal. The RF wake-up circuit 61 thensends a wake-up enable signal to the RF decode circuit 62. The RF decodecircuit 62, via the antenna 63, translates it into a series of bits andthen sends the digital bitstream signal to the processing electronics 65to determine if the digital bitstream signal contains the access code.

[0076] In another embodiment, the RF wake-up circuit 61 remains in lowpower sleep mode until it senses the RF signal. The RF signal, in thisembodiment, contains a low carrier frequency way and a high frequency RFbitstream superimposed on the low frequency carrier wave. When the RFwake-up circuit 61 senses, via the antenna 66, that there is a signaltuned to the low frequency carrier wave, the RF wake-up circuit 61 sendsa wake-up enable signal to the RF decode circuit 62. The RF decodecircuit 62 then accepts the RF bitstream access code signal, andtranslates it into a series of bits for the microprocessor 14.

[0077]FIG. 7 shows the schematic of the input electronics 60 wherein theRF wake-up circuit 61 periodically wakes up from a low power sleep modeand senses if there is an incoming RF signal. The RF wake-up circuit 61consists of two low-power CMOS inverter gates, INV1 and INV2, a CMOStransistor Q3, resistors, and a capacitor. The two inverters INV1 andINV2 are configured in an oscillator configuration in a ratio of 1 to100. In other words, the oscillator will switch on for {fraction(1/100)} of a second. At this time, the CMOS transistor Q3 will turn onand supply the battery power to the RF decode circuitry 62. The RFdecode circuitry 62 will only draw battery power for {fraction (1/100)}of the time, and thus the battery will last 100 times longer than if thebattery were permanently connected to the RF decode circuitry 62.

[0078] The RF decode circuitry 62 consists of two bipolar junctiontransistors Q1, Q2, two Operational Amplifiers, OP1 and OP2, andresistors, capacitors, inductors and diodes connected to thesecomponents. The RF input signal is referred to as an on-off keying ofhigh frequency bursts for set time frames. In the present invention, thefrequency is set at 320 MHz. A burst of frequency is detected by the Q1and Q2 transistors with their circuits tuned to the correct frequency(320 MHz in this example). The RF decode circuitry 62 then senses thedata bitstream sent in the form of digital 1 data signal and digital 0dead band of no frequency. Thus, a train of on and off frequency pulseswould be received by the antenna, conditioned and amplified by Q1 and Q2of the RF decode circuitry 62, and converted to bitstream 1 and 0digital signals by the two operational amplifier signal conditioners OP1and OP2.

[0079] Typically, the operator of the control unit 59 which contains theRF transmitter will enable the RF transmitter with a transmit button 58to send an RF on-off keying pulse for approximately one second. The RFsignal being transmitted is a digital bitstream conditioned to an RFon-off keying signal which takes about two milliseconds in which totransmit one complete signal. The control unit 59 then repeats thesignal over and over for the duration that the RF transmitter isenabled. In order for the receiver to detect one complete bitstream fromthe transmitter, the RF signal only needs to be sampled for twomilliseconds during which the transmitter is enabled and transmitting.If the RF transmitter is enabled for one second, the transmittedbitstream signal takes {fraction (1/500)} of a second to be transmittedand is repeated 500 times over the entire one second. The receiver isenabled for {fraction (1/100)} of a second every second, and will havethe opportunity to sample and detect a signal that is {fraction (1/500)}of a second in duration, transmitted 500 times over one second. Afterthe {fraction (1/100)} of a second, the oscillator, formed by INV1 andINV2, will switch Q3 off, and the battery power to the RF decodecircuitry will be shut off. Only the oscillator circuit (INV1 and INV2)will dissipate battery power at a small rate of less than 100micro-amps.

[0080] If less power dissipation by the RF decode circuitry 62 isrequired, the decode circuitry power duty cycle can be reduced byincreasing the oscillator frequency to more than 100 to 1 and thusdecreasing the RF decode circuitry 62 sample rate. In order to ensurethe RF decode circuitry 62 will be enabled long enough to detect theentire transmitter digital bitstream, the lock CPU would wait for thebeginning of the bitstream signal which is received by the RF decodecircuitry 62 when the circuitry was enabled and conditioned through OP1,and then would send an output enable signal back to Q3 to override theoscillator and keep the RF decode circuitry 62 enabled with batterypower until the lock CPU has received the correct amount of bitstreamdata from the transmitter through the decode circuitry. Thereafter, thelock CPU would disable the Q3 transistor and the RF decode circuitry andlet the oscillator go back to its low rate of sampling.

[0081] The processing electronics 64 remains in sleep-mode low currentoperation until a valid on-off keying frequency signal is received whilethe RF decode circuitry is enabled and a digital bitstream signal issent to the lock microprocessor 65. Upon transferring the bitstreamsignal, the microprocessor 14, within the processing electronics,compares the input code with the access code in the comparator. Ifcorrect, the solenoid, DC motor, electromechanical relay, or solid-staterelay is activated. After this operation, the microprocessor 14 sends adisable signal to the RF wake-up circuit to assume a low power mode.

[0082]FIG. 8 shows the schematic of another embodiment of the electronicaccess control device which also multiplexes the inputs and outputs ofthe pins of the microprocessor to reduce the number of pins required.The microprocessor 81 used in this embodiment is preferably theMC68HRC705J1A integrated circuit (IC) manufactured by Motorola. Asillustrated in FIG. 8, the input devices include a keypad 11 and anelectronic key reader 82.

[0083] In this embodiment, instead of using an EPROM internal of themicroprocessor as in the case of the embodiment of FIG. 3, an EEPROM 84external of the microprocessor 81 is used to store the programmed accesscode as well as other useful information. The EEPROM 84 used in thisembodiment is preferably the 93LC46 IC manufactured by Microchip.Alternatively, a FLASH read-write memory, or any other type of suitablememory, may be used. To effectively use the limited number of pins ofthe microprocessor 81, the pins are multiplexed such that the keypad 11and the EEPROM 84 share several communication pins. As illustrated inFIG. 8, pins 16 (PA2), 17(PA1), 18 (PA0) of the microprocessor 81 areconnected to pins 4,3, and 2 of the EEPROM 84, respectively. These pinsof the microprocessor 81 are also connected to the keypad 11 forreceiving access codes entered by means of the keypad. Pin 3 (PB5) ofthe microprocessor 81 is connected to pin 1 of the EEPROM. In thisconfiguration, pins 1-4 of the EEPROM 84 are used, respectively, forchip select, data in, data out, and clock.

[0084] In accordance with an aspect of the present invention, themicroprocessor-based control circuit further includes a low-batterydetection circuit 68 that does not consume electrical power except whena low-battery detection is in progress. As illustrated in FIG. 8, theaccess control device is powered by a battery pack 70 which includes oneor more batteries. The output of battery pack is connected to a voltageregulator 72 which provides a regulated voltage for operating thecontrol circuit. The low-voltage detection circuit 68 includes a voltagedivider 74 which has its input end connected to the output of thebattery pack 70 (which in the illustrated case is after an isolatingdiode 71). The voltage divider 74 is connected in series with atransistor 76 to ground. The base of the transistor 76 is connected (viaa resister 77) to pin 6 (PB2) of the microprocessor 81. When Pin 6 ofthe microprocessor 81 is set high, the transistor 76 is turned on,thereby allowing current to flow through the voltage divider 74. Whenpin 6 is set low, the transistor 76 is turned off, and the currentthrough the voltage divider is cut off. In that case, the output voltageof the voltage divider 74 will be pulled up to that of the batteryvoltage minus the voltage drop across the diode 71.

[0085] The output end of voltage divider 74 is connected to the base ofa second transistor 80. The input end of the transistor 80 is connectedto the output of the voltage regulator 72, while the output end of thetransistor 80 is connected to pin 15 (PA3) of the microprocessor 81.Normally pin 6 of the microprocessor would stay low, and both thetransistor 76 and the transistor 80 would be turned off. When a batteryvoltage test is performed, pin 6 is switched to the high (“1”) state toturn on the transistor 76, and the state of pin 15 is sensed by themicroprocessor 81 to determine the on/off state of the transistor 80. Ifthe battery voltage is sufficiently high, the output of the voltagedivider 74 would be high enough to turn the transistor 80 off. On theother hand, if the battery voltage is low, the output of the voltagedivider would be low enough to turn the transistor 80 on, and pin 15would be switched to the high state.

[0086] In accordance with an important aspect of the present invention,there is provided an electronic access control device that providessubstantially enhanced security and reduced vulnerability to tamperingby using two microprocessors. FIG. 9 shows generally the functionalblock diagram of such a device. As illustrated in FIG. 9, the controldevice has a first microprocessor 90 and a second microprocessor 92. Thefirst microprocessor 90 is connected to an input device 94 for receivinga user-entered control signal signifying a demand to operate anelectronic device 98. The second microprocessor 92 controls a drivercircuit 96 for energizing the electrical device 98 to effect a desiredoperation. The electrical device 98 may be, for example, a solenoid,motor, relay, or the like for opening a lock, or, as will be describedin greater detail below, the ignition relay of a motorcycle. The firstmicroprocessor 90 may be positioned close to the input device 94, whilethe second microprocessor 92 may be located close to the electricaldevice 98 and is preferably well shielded from external access. The twomicroprocessors are connected by a two-way communication link 100.

[0087] As will be described in greater detail below, the user-enteredcontrol signal may be, for example, an access code entered using akeypad or electronic key, the operation of an electronic ignition switchcontrolled by a mechanical lock, or a voice command entered through avoice sensor such as a microphone. Once a user-entered control signal isreceived, the first microprocessor 90 determines whether the demand tooperate the electrical device 98 should be transmitted to the secondmicroprocessor 92. If the demand is to be transmitted, the firstmicroprocessor 90 sends a special communication code to the secondmicroprocessor 92 via the communication link 100. The secondmicroprocessor 92 compares the transmitted communication code with apreset communication code stored in a non-volatile memory 102. If thetransmitted code matches the stored code, the second microprocessor 92activates the driver circuit 96 to energize the electrical device 98.

[0088] It will be appreciated that this dual-microprocessorconfiguration significantly reduces the vulnerability of the device totampering. Even if a tamperer may gain access to the firstmicroprocessor, it is intended that the second microprocessor is wellshielded and therefore cannot be reached easily. Since the secondmicroprocessor responses only to a correct communication code, thetamperer will not be able to use the trick of “hot-wiring” to activatethe driver circuit 96.

[0089] Moreover, even if the circuit containing the first microprocessoris somehow replaced by another similar microprocessor circuit for whichthe correct control signal is already known, that new microprocessor isunlikely to know the communication code specific to the secondmicroprocessor 92. In this way, the two microprocessors function as twoindividual gate keepers. Even if the first microprocessor could besomehow bypassed, the second microprocessor would not activate thedriver circuit without receiving the correct communication code.

[0090] The microprocessors can also be programmed to implement the“code-hopping” or “rolling-code” scheme used in some existing electronicaccess control devices to further improve the security of the device. Insuch a scheme, the preset code stored in the non-volatile memory 102 isused as a seed, and the communication codes stored in the first andsecond microprocessors are changed as a function of the number of codetransmission according to a predefined algorithm based on the seed code.The changes of the communication codes in the two microprocessors aresynchronized so that the they remain in operative relationship.

[0091]FIGS. 10A and 10B illustrate an application of thedual-microprocessor configuration in an electronic lock. In thisembodiment, the control circuit has two halves connected by a cable. Thefirst half, which is shown in FIG. 10A, contains a first microprocessor110. The second half, shown in FIG. 10B, contains a secondmicroprocessor 112. Pin 11 (PA7) of the first microprocessor 110 isconnected to pin 18 (PA0) of the second microprocessor 112 via the cable115 and the mating connectors 114 and 116 to establish a two-way serialcommunication channel between the two microprocessors.

[0092] The electronic lock has a keypad 11 and an electronic key reader82 as input devices which are connected to the first microprocessor 110.The second microprocessor 112 controls a energizing circuit 118 forenergizing a solenoid 120 to open the lock. When the firstmicroprocessor 110 receives an access code via either the keypad 11 orthe key reader 82, it compares the entered access code with an accesscode stored in its memory. If the entered code matches the stored accesscode, the first microprocessor 110 transmits a communication code to thesecond microprocessor 112 via the communication channel described above.The second microprocessor 112 then compares the received communicationcode with a preset communication code stored in an EEPROM 122. If thetwo communication codes match, the second microprocessor 112 activatesthe energizing circuit 118 to energize the solenoid 120 to open thelock.

[0093] The correct access code and communication code are preferablystored in the EEPROM 122. During initial power-up, i.e., when thebattery is first attached to the electronic lock, the secondmicroprocessor 112 transmits the access code and the communication codeto the first microprocessor 110, which then stores the codes in itsmemory (which may be volatile) for subsequent operation.

[0094] The dual-microprocessor configuration illustrated in FIG. 9 canalso be advantageously used in other types of applications. For example,FIG. 11 shows an electronic ignition control system for a motorcycle. Inthis embodiment, the device contains a first microprocessor 126 and asecond microprocessor 128 which are connected by a cable 130. Athree-position ignition switch 132 is connected to the firstmicroprocessor 126, which may be located close to the ignition switch.The second microprocessor 128 is connected to an ignition relay 134 andan accessory relay 138, and is preferably disposed close to the ignitionmechanism of the motorcycle and well protected from external access.

[0095] In this arrangement, the ignition switch 132 serves as the inputdevice, and the position of the ignition switch is used as theuser-entered control signal. The first microprocessor 126 monitors theswitch position. When the ignition switch 132 is turned to the“accessory” position 135, the first microprocessor 126 transmits acommunication code together with a switch-position code corresponding tothat switch position to the second microprocessor 128. The secondmicroprocessor 128 compares the transmitted communication code with apreset communication code stored in a non-volatile memory 138 which hasbeen programmed at the factory. If the two codes match, the secondmicroprocessor 128 determines from the switch-position code that theswitch is set at the accessory position and closes the accessory relay136.

[0096] Similarly, when the ignition switch 132 is turned to the“ignition” position 133, the first microprocessor 126 transmits acommunication code and a switch-position code corresponding to theignition position to the second microprocessor 128. The secondmicroprocessor 128 compares the transmitted communication code with thepreset communication code. If the two codes match, the secondmicroprocessor 128 determines from the switch-position code that theswitch is set at the ignition position and accordingly closes theignition relay 134 and the accessory relay 136 to start the engine.

[0097] It will be appreciated that due to this dual-microprocessorarrangement, this ignition control system cannot be “hot-wired” to startthe engine of the motorcycle like conventional motorcycle ignitioncontrol systems. This system is also not susceptible to tampering byreplacing the assembly of the ignition switch 132 and the firstmicroprocessor 126 with another such assembly for which an ignition keyhas been obtained.

[0098]FIGS. 12-14 show another advantageous application of thedual-microprocessor configuration of FIG. 9 which utilizes speechrecognition to control the operation of an electronic access controldevice. As illustrated in FIG. 12, the access control device uses aspeech recognition microcomputer integrated circuit (IC) 200 to processvoice commands given by a user. The speech recognition IC 200 is capableof not only recognizing the commands given but also the voice of thespeaker. In other words, the IC is capable of speaker dependentrecognition, allowing the user to customize the words to be recognized.Such an IC may be, for example, the RSC-164 microcomputer of SentryCircuits, Inc.

[0099] In the embodiment shown in FIG. 12, the speech recognition IC 200has a microphone 202 connected thereto for receiving voice commands froma user. In this embodiment, the combination of the voice recognition IC200 and the microphone 202 serves generally the function of the inputdevice 94 of FIG. 9. An optional keypad 11 may also be used for enteringan access code. After receiving a voice command, the speech recognitionIC 200 analyzes the voice command to recognize the command and the voicepattern of the speaker. If the voice recognition IC 200 recognizes thevoice pattern to be that of an authorized user, it transmits a commandcode corresponding to the command received to the first microprocessor190. The first microprocessor 190 transmits an operation codecorresponding to the command and a communication code stored in itsmemory to the second microprocessor 192 via a bidirectionalcommunication link 180. The second microprocessor 192 compares thetransmitted communication code with a preset communication code which isstored in a non-volatile memory 194. If the two communication codesmatch, the second microprocessor 192 activates the driver circuit 196 toenergize an electrical device 198 to carry out the operation specifiedby the operation code.

[0100]FIG. 13 shows another embodiment of the voice controlled accesscontrol device. In this embodiment, the voice recognition IC 200, whichis a microcomputer in itself, is used to serve the function of the firstmicroprocessor 190 of FIG. 12. Upon receiving a voice command throughthe microphone 202, the voice recognition IC 200 recognizes the commandand analyzes the voice pattern of the speaker. If the voice recognitionIC 200 determines that the speaker is an authorized user, it transmitsan operation code and a communication code stored in its memory 201 tothe second microprocessor 192. If the transmitted communication codematches a preset communication code, the second-microprocessor 192executes the command by activating the driver circuit 196.

[0101]FIG. 14 shows another embodiment of the voice operated accesscontrol device which includes a central control station 220 and one ormore remote devices in the arrangement shown generally in FIG. 6. Thecentral control station 220 may be formed as a hand-held remote controlunit which can be conveniently carried and handled by the user. Forillustration purposes, two remote devices 212A, 212B are shown, each ofwhich has its own unique identification code. The identification codesare stored in the memories 216A, 216B of the microprocessors 228A, 228Bof the respective remote devices. The central control station 220 has avoice recognition IC 200 coupled to a microphone 202 for receiving andrecognizing a voice command. If the voice pattern of the speaker matchesa voice pattern stored in the voice recognition IC 200, the voicerecognition IC transmits a command code corresponding to the givencommand to a central microprocessor 222. The command code may contain acode to indicate which remote device is to be contacted. Alternatively,the determination of which remote device is to be contacted may be madeby the central microprocessor according to the command code provided bythe voice recognition IC 200.

[0102] The central microprocessor contains a memory 224 which has theidentification codes for the remote devices stored therein. Afterreceiving the command code, the central microprocessor 222 sends outthrough the transmitter circuit 226 a bitstream signal which containsthe identification code of the remote device to be addressed and anoperation code indicating the operation to be performed. In thepreferred embodiment, the bitstream signal is transmitted at a radiofrequency (RF). Other suitable transmission bands may also be used.

[0103] The remote devices 212A, 212B preferably are normally in thesleep mode and can wake up in the ways described in conjunction withFIG. 6. In the illustrated embodiment, each remote device has a wake-upcircuit 230A, 230B and a radio frequency decode circuit 232A, 232B.After receiving the bitstream signal from the central control station220, the radio frequency decode circuit of each remote device convertsthe received RF signal into a computer-compatible binary code whichincludes the identification code and the operation code. Each remotedevice then compares the received identification code with its ownidentification code. If the codes match, the remote device carries outthe specified operation.

[0104] This voice-activated remote access control system finds manyapplications in different settings. For example, as illustrated in FIG.14, the remote access control device 212A is connected to a file cabinet240 and a desk 242 in an office for locking and unlocking the cabinetdrawers and desk drawers. By way of example, when the user gives thevoice command “lock desk,” the central control station 220 receives thecommand through the microphone 202. If the speaker's voice isrecognized, the central control station 220 sends out a bitstream signalto cause the remote unit 212A to operate a lock mechanism 241 in thedesk 240 to lock the desk drawers. As another example illustrated inFIG. 14, the remote device 212B is used to control a motor 243 in a toolchest 244 to lock and unlock the doors and drawers of the tool chest.

[0105] In accordance with the object of the present invention to preventthe unauthorized use of electronic keys, there is provided an electronicaccess control system which has a plurality of remote electronic locksand a master key that has a number of access programmed therein. Asillustrated in FIG. 15, the access control system includes a mastercontrol device 140 for programming a master access code and the desirednumber of access into the master key 142. In the illustrated embodiment,the master control device 140 is a personal computer which has aninterface device 144, such as a key reader, for communicating with themaster key. The master key 142 contains a non-volatile memory whichincludes an access code storage 146 for storing the master access codespecific to the control system, and a counter 148 for storing the numberof access allowed. Also shown in FIG. 15 is an electronic lock 150 whichcan be opened by the master key. The electronic lock has a controlcircuit based on a microprocessor 151 and a key reader 152 forcommunicating with the master key. When the master key 142 is presentedto the key reader 152, the microprocessor 151 of the electronic lockreads the access code stored in the master key and compares that code toa preset master access code stored in its memory. If the two codesmatch, the control circuit reads the number of access stored in themaster key. If the number of access is one or greater, themicroprocessor 151 energizes the solenoid 154 to open the lock 156. Inconjunction with the opening of the lock, the microprocessor 151 of theelectronic lock 150 decrements the number of access stored in thecounter 148 of the master key by one. Thus, if the number of access inthe counter 148 is initially set to one, after the opening of the lockthe counter is reduced to zero, and the master key cannot be used toopen another lock.

[0106] In this way, by limiting the number of times the master key 142can be used to open locks, the unauthorized use of the master key iseffectively prevented. For instance, in the setting of a hotel, it isnecessary to have a mater key for opening the electronic locks installedin the safes in the hotel rooms. If a hotel guest forgets the accesscode for the safe in his room, the master key can be programmed with thenumber of access set to one, and used to open that safe. Since thenumber of access will be reduced to zero after the lock is opened, themaster key cannot be subsequently used to open the safe in another room.The use of the master key is thus strictly controlled.

[0107] In accordance with another aspect of the invention, there isprovided an alarm system for a bicycle or a similar manually poweredvehicle. As illustrated in FIG. 15, this alarm system includes a remotecontrol 160 mounted in the helmet 162 of the rider of the bicycle 166,and an electronic alarm 164 mounted on the bicycle. The remote control160 has a transmitter 168 for the wireless transmission of acommunication code and other types of control signals to the alarm 164on the bicycle, which has a receiver 170 for receiving the transmittedsignals.

[0108] In the preferred embodiment, the remote control 160 has a button172 which when pushed transmits a control signal including thecommunication code to the alarm 164 on the bicycle to activate ordeactivate the alarm. Alternatively, the helmet may be equipped with akeypad for entering an access code by the user. After receiving theaccess code, the remote control compares the entered access code with apreset access code and transmits the control signals to the electronicalarm on the bicycle when the two access codes match.

[0109] The alarm 164 includes a motion detector 174 for sensing themovement of the bicycle 166. If movement of the bicycle is detected bythe motion detector 174 when the alarm has been activated, theelectronic alarm 164 emits audio and/or visual warning signals to deterthe potential theft. A timer 176 is included in the electronic alarm 164to stop the warning signals after a predetermined amount of time haselapsed.

[0110] This bicycle alarm system which has a remote control 172 mountedin the riding helmet 162 has many advantages. Combining the remotecontrol with the riding helmet provides significant convenience to therider because there is no need to carry the remote control separately.Moreover, because the remote control is integrated in the helmet of therider, the rider is less likely to lose or misplace the remote control.Furthermore, because the remote control is required to deactivate thealarm system, combining the remote control with the helmet provides anincentive for the rider to wear the helmet when riding the bicycle. Inthis way, the bicycle alarm system of the present invention contributesto the safety of the rider and helps the rider to obey the law requiringthe bicycle rider to wear a helmet.

We claim:
 1. A method comprising the steps of: deactivating a circuitduring a first time period; enabling a portion of the circuit for asecond time period; sensing an electromagnetic signal during the secondtime period; enabling the circuit for an extended time period that isgreater than the second time period upon the sensing of theelectromagnetic signal; processing the electromagnetic signal during theextended time period to obtain an input code; comparing the input codeto an access code; and, providing a signal to unlock a device if theinput code matches the access code.
 2. The method of claim 1, furthercomprising the step of generating an oscillation signal and deactivatingthe circuit in response to the oscillation signal.
 3. The method ofclaim 1, further comprising the step of toggling a switch to enable thecircuit for the extended time period.
 4. The method of claim 1, furthercomprising the step of operating at least one of the following inresponse to the signal to unlock the device: an electromechanicaldriver; a solenoid; a DC motor; an electromechanical relay; and, asolid-state relay.
 5. The method of claim 1, wherein the electromagneticsignal is infrared.
 6. The method of claim 1, wherein theelectromagnetic signal is within a radio frequency.
 7. The method ofclaim 1, further comprising the step of activating another portion ofthe circuit to compare the input code to an access code.
 8. A methodcomprising the steps of: periodically enabling and disabling a circuitduring each of a plurality of duty cycles wherein the circuit is enabledfor a time t₁ during each of the duty cycles; receiving an input codetransmitted via an electromagnetic signal; comparing the input code toan access code; enabling the circuit as the input code is being receivedfor a time t₂ that is greater than said time t₁; and, providing a signalto unlock a device if the input code matches the access code.
 9. Themethod of claim 8, further comprising the step of sensing receipt of theelectromagnetic signal.
 10. The method of claim 8, wherein theelectromagnetic signal is infrared.
 11. The method of claim 8, whereinthe electromagnetic signal is within a radio frequency.
 12. The methodof claim 8, further comprising the step of generating an override signalduring at least a portion of the step of enabling the circuit as theinput code is being received.
 13. The method of claim 8, furthercomprising the step of toggling a switch during at least a portion ofthe step of enabling the circuit as the input code is being received.14. The method of claim 8, further comprising the step of operating atleast one of the following in response to the signal to unlock thedevice: an electromechanical driver; a solenoid; a DC motor; anelectromechanical relay; and, a solid-state relay.
 15. A method foroperating a circuit on current drained from a battery comprising thesteps of: generating a signal to indicate detection of a device capableof providing an electromagnetic signal; receiving an input codetransmitted by the electromagnetic signal; increasing the currentdrained from the battery; comparing the input code to an access code;providing an output to an unlock device if the input code matches theaccess code; and, decreasing the current drained from the battery afterreceiving the input code.
 16. The method of claim 15, further comprisingthe step of increasing the current drained from the battery comprisingtoggling a switch and the step of decreasing the current drained fromthe battery comprising toggling the switch.
 17. The method of claim 15,further comprising the step of generating an oscillation signal duringthe step of receiving the input code.
 18. The method of claim 15,wherein the electromagnetic signal is infrared.
 19. The method of claim15, wherein the electromagnetic signal within a radio frequency.
 20. Themethod of claim 15, further comprising the step of operating at leastone of the following in response to the signal to unlock the device: anelectromechanical driver; a solenoid; a DC motor; an electromechanicalrelay; and, a solid-state relay.